The invention relates in particular to a valve of the type described in copending patent application Ser. No. 08/057,211, filed May 3, 1993, which is a continuation of application Ser. No. 07/718,605, filed Jun. 21, 1991, now abandoned.
Essentially, this type of heart valve consists of a ring which encloses hinged curved wings. The ring has diametrically opposite fixtures designed to offset the means of hinging the wings so that in their maximum opened position of at least 85.degree., the latter only project beyond the plane of the ring by a small amount thus delimiting, in conjunction with the shape of the wings, three equivalent areas allowing a laminar, axial central flow. The means of hinging the said wings are integrated in the thickness of the ring so that the ends of the wings, at the level of the fixtures, are spread apart, thus delimiting a space which is completely unobstructed in order not to limit or interfere with the central flow.
According to the invention, an attempt has been made to improve these basic characteristics. In particular, it became apparent that at the instant the wings close, the latter tap slightly against the internal periphery of the ring. Taking into account frequencies of beating and, consequently, the opening and closing cycle of the wings, this can produce wear in the area where the wings come into contact with the body of the ring.
In addition, at the level of this contact area, in the closed positions of the wings, i.e. when they press against the ring, this produces a reaction force which is transmitted directly at the level of the hinge axis. The effect of this reaction force acts on the hinging of the wings.
The invention intends to overcome these drawbacks in a simple, reliable, effective and rational manner.
One of the problems which the invention aims to solve is to eliminate any reaction force likely to act on the hinging of the wings on the one hand and to prevent any wear at the level of the ring on the other hand. The intention is therefore to prevent the forces generated when the wings close in the contact area with the ring, from stressing the hinge part of the wings and resulting in wear of the wings at the level of this contact area. It is important to obtain a damping effect intended to reduce noise and wear taking into account the problems of fluid flow efficiency without interfering with the flow of blood.
In order to solve such a problem, the ring has an internal peripheral fixture in the form of a hollow imprint which matches the external shape of the edge of the wing and of which the cross-section consists of a curved profile provided by moving the external edge of the wings to their closed position, thus creating an end-stop effect.
Another problem which the invention aims to solve is to provide an end stop in the maximum opened position of the wings in a simple and effective manner with the intention of rationalising manufacture.
Such a problem is resolved by the fact that the fixtures have means of locking the wings in their opened position in the form of a separately mounted pad fixed so that it projects beyond the internal surface of the ring between the hinge parts of the said wings.
Another problem which the invention aims to solve is to simplify the hinge of the wings on the corresponding parts of the ring. In this regard, it should be noted that the means of hinging the wings consist of parts having a male hemispherical shape at each end which project beyond the profile of each wing and fit in the matching hemispherical recesses.
According to the invention and making allowance for the problem to be solved, the hemispherical recesses are formed in separately mounted studs integrated in the thickness of the ring which act as a bearing.
Ideally, the studs are cylindrical and are fixed in the matching receptacles formed in the thickness of the ring.
Another problem which the invention aims to solve is to optimize the hinge torque.
Such a problem is solved by the fact that the studs are made of a monocrystalline ceramic (meaning formed from a single crystal and thereby exhibiting uniform properties throughout) or any other material having a low coefficient of friction.
Note that this solution of separately mounted bearing surfaces for hinging the wings is particularly useful for rationalising manufacture and for obtaining surface finishes of excellent quality. In addition, it is possible to select the most appropriate material which, in particular, may be different from the material of which the ring and/or wing is/are made.